"First point: you can divide z^n by (x-y) with x^n-1 + yx^n-2 + y^2x^n-3 +... y^n-1" ...Uuh? Of course, we're already ruling out , but then
, so what is the term above?
Certainly , but this is true only if is odd, and
anyway we don't have , so what was intended here?